Generally, an IC device may include high or low voltage devices (e.g., transistors) that can provide different functionalities and have different applications. Also, an IC device can be designed as a system on chip (SoC), which may include a combination of mixed-signal, digital, or analog circuits for implementing radio frequency (RF), memory, logic, high voltage interface, and the like functionalities. IC devices may have applications in automotive, mobile electronics, medical, or other technology areas, wherein various voltage or signal levels may be present. In some applications, digital circuits would require analog or high voltage interface circuits that would be associated with high voltage inputs as well as high gate drive voltages. Usually, high voltage devices, such as high voltage complementary metal-oxide-semiconductor (CMOS) devices, are fabricated via different processes than processes used in the fabrication of lower voltage devices. For example, high voltage devices may require additional processing or masking steps as well as a need to be fabricated at a different scale (e.g., 180 or 130 nanometer (nm)) when compared to more advanced processes to fabricate FINFET type devices at 65, 55, 45 nm or lower scales.
FIGS. 1A and 1B schematically illustrate planar transistor and FINFET structure, respectively, in example IC devices. Adverting to FIG. 1A, a conventional planar metal-oxide-semiconductor field-effect-transistor (MOSFET) is illustrated, which includes a silicon substrate 101, a silicon layer 103, a source region 105, a drain region 107, and a logic gate that includes a poly-silicon layer 109 on a layer of gate oxide 110.
FIG. 1B illustrates an example IC device that includes a FINFET type transistor and a vertical fin 111, which includes a source region 111a and a drain region 111b, and a logic gate (e.g., a trigate) that includes a poly-silicon vertical structure 113 that wraps around a layer of gate oxide 110, which wraps around the top and sidewall surfaces of the fin 111 for controlling a current flow from the source region to the drain region of the fin.
FIG. 1C illustrates a cross-sectional view of the IC device of FIG. 1A along line 1A-1A′ where an application of a voltage to the logic gate 109 creates a channel between the source and drain regions that allows for a current 115 to flow from the source region to the drain region. An important parameter of the device can be its breakdown voltage, which is the voltage (e.g., between the source and drain regions) that the device can withstand without damage to its circuitries. Additionally, leakage current between the source and drain regions as well as between adjacent devices can affect efficiency of an IC device. The leakage current may be a function of application of a voltage, where a high voltage at a device may cause high leakage current in a surrounding area in the device. As noted, among considerations in designing and fabricating high voltage transistors are the additional fabrication process steps and the potential leakage currents in an IC device.
A need therefore exists for a methodology for designing and making high voltage IC devices utilizing a fin-type process with protection against potential leakage current and the resulting device.